• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
4  */
5 
6 #include <linux/dcache.h>
7 #include <linux/fs.h>
8 #include <linux/gfp.h>
9 #include <linux/init.h>
10 #include <linux/module.h>
11 #include <linux/mount.h>
12 #include <linux/srcu.h>
13 
14 #include <linux/fsnotify_backend.h>
15 #include "fsnotify.h"
16 
17 /*
18  * Clear all of the marks on an inode when it is being evicted from core
19  */
__fsnotify_inode_delete(struct inode * inode)20 void __fsnotify_inode_delete(struct inode *inode)
21 {
22 	fsnotify_clear_marks_by_inode(inode);
23 }
24 EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
25 
__fsnotify_vfsmount_delete(struct vfsmount * mnt)26 void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
27 {
28 	fsnotify_clear_marks_by_mount(mnt);
29 }
30 
31 /**
32  * fsnotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
33  * @sb: superblock being unmounted.
34  *
35  * Called during unmount with no locks held, so needs to be safe against
36  * concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block.
37  */
fsnotify_unmount_inodes(struct super_block * sb)38 static void fsnotify_unmount_inodes(struct super_block *sb)
39 {
40 	struct inode *inode, *iput_inode = NULL;
41 
42 	spin_lock(&sb->s_inode_list_lock);
43 	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
44 		/*
45 		 * We cannot __iget() an inode in state I_FREEING,
46 		 * I_WILL_FREE, or I_NEW which is fine because by that point
47 		 * the inode cannot have any associated watches.
48 		 */
49 		spin_lock(&inode->i_lock);
50 		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
51 			spin_unlock(&inode->i_lock);
52 			continue;
53 		}
54 
55 		/*
56 		 * If i_count is zero, the inode cannot have any watches and
57 		 * doing an __iget/iput with SB_ACTIVE clear would actually
58 		 * evict all inodes with zero i_count from icache which is
59 		 * unnecessarily violent and may in fact be illegal to do.
60 		 * However, we should have been called /after/ evict_inodes
61 		 * removed all zero refcount inodes, in any case.  Test to
62 		 * be sure.
63 		 */
64 		if (!atomic_read(&inode->i_count)) {
65 			spin_unlock(&inode->i_lock);
66 			continue;
67 		}
68 
69 		__iget(inode);
70 		spin_unlock(&inode->i_lock);
71 		spin_unlock(&sb->s_inode_list_lock);
72 
73 		if (iput_inode)
74 			iput(iput_inode);
75 
76 		/* for each watch, send FS_UNMOUNT and then remove it */
77 		fsnotify_inode(inode, FS_UNMOUNT);
78 
79 		fsnotify_inode_delete(inode);
80 
81 		iput_inode = inode;
82 
83 		cond_resched();
84 		spin_lock(&sb->s_inode_list_lock);
85 	}
86 	spin_unlock(&sb->s_inode_list_lock);
87 
88 	if (iput_inode)
89 		iput(iput_inode);
90 	/* Wait for outstanding inode references from connectors */
91 	wait_var_event(&sb->s_fsnotify_inode_refs,
92 		       !atomic_long_read(&sb->s_fsnotify_inode_refs));
93 }
94 
fsnotify_sb_delete(struct super_block * sb)95 void fsnotify_sb_delete(struct super_block *sb)
96 {
97 	fsnotify_unmount_inodes(sb);
98 	fsnotify_clear_marks_by_sb(sb);
99 }
100 
101 /*
102  * Given an inode, first check if we care what happens to our children.  Inotify
103  * and dnotify both tell their parents about events.  If we care about any event
104  * on a child we run all of our children and set a dentry flag saying that the
105  * parent cares.  Thus when an event happens on a child it can quickly tell if
106  * if there is a need to find a parent and send the event to the parent.
107  */
__fsnotify_update_child_dentry_flags(struct inode * inode)108 void __fsnotify_update_child_dentry_flags(struct inode *inode)
109 {
110 	struct dentry *alias;
111 	int watched;
112 
113 	if (!S_ISDIR(inode->i_mode))
114 		return;
115 
116 	/* determine if the children should tell inode about their events */
117 	watched = fsnotify_inode_watches_children(inode);
118 
119 	spin_lock(&inode->i_lock);
120 	/* run all of the dentries associated with this inode.  Since this is a
121 	 * directory, there damn well better only be one item on this list */
122 	hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
123 		struct dentry *child;
124 
125 		/* run all of the children of the original inode and fix their
126 		 * d_flags to indicate parental interest (their parent is the
127 		 * original inode) */
128 		spin_lock(&alias->d_lock);
129 		list_for_each_entry(child, &alias->d_subdirs, d_child) {
130 			if (!child->d_inode)
131 				continue;
132 
133 			spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
134 			if (watched)
135 				child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
136 			else
137 				child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
138 			spin_unlock(&child->d_lock);
139 		}
140 		spin_unlock(&alias->d_lock);
141 	}
142 	spin_unlock(&inode->i_lock);
143 }
144 
145 /* Are inode/sb/mount interested in parent and name info with this event? */
fsnotify_event_needs_parent(struct inode * inode,struct mount * mnt,__u32 mask)146 static bool fsnotify_event_needs_parent(struct inode *inode, struct mount *mnt,
147 					__u32 mask)
148 {
149 	__u32 marks_mask = 0;
150 
151 	/* We only send parent/name to inode/sb/mount for events on non-dir */
152 	if (mask & FS_ISDIR)
153 		return false;
154 
155 	/*
156 	 * All events that are possible on child can also may be reported with
157 	 * parent/name info to inode/sb/mount.  Otherwise, a watching parent
158 	 * could result in events reported with unexpected name info to sb/mount.
159 	 */
160 	BUILD_BUG_ON(FS_EVENTS_POSS_ON_CHILD & ~FS_EVENTS_POSS_TO_PARENT);
161 
162 	/* Did either inode/sb/mount subscribe for events with parent/name? */
163 	marks_mask |= fsnotify_parent_needed_mask(inode->i_fsnotify_mask);
164 	marks_mask |= fsnotify_parent_needed_mask(inode->i_sb->s_fsnotify_mask);
165 	if (mnt)
166 		marks_mask |= fsnotify_parent_needed_mask(mnt->mnt_fsnotify_mask);
167 
168 	/* Did they subscribe for this event with parent/name info? */
169 	return mask & marks_mask;
170 }
171 
172 /*
173  * Notify this dentry's parent about a child's events with child name info
174  * if parent is watching or if inode/sb/mount are interested in events with
175  * parent and name info.
176  *
177  * Notify only the child without name info if parent is not watching and
178  * inode/sb/mount are not interested in events with parent and name info.
179  */
__fsnotify_parent(struct dentry * dentry,__u32 mask,const void * data,int data_type)180 int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
181 		      int data_type)
182 {
183 	const struct path *path = fsnotify_data_path(data, data_type);
184 	struct mount *mnt = path ? real_mount(path->mnt) : NULL;
185 	struct inode *inode = d_inode(dentry);
186 	struct dentry *parent;
187 	bool parent_watched = dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED;
188 	bool parent_needed, parent_interested;
189 	__u32 p_mask;
190 	struct inode *p_inode = NULL;
191 	struct name_snapshot name;
192 	struct qstr *file_name = NULL;
193 	int ret = 0;
194 
195 	/*
196 	 * Do inode/sb/mount care about parent and name info on non-dir?
197 	 * Do they care about any event at all?
198 	 */
199 	if (!inode->i_fsnotify_marks && !inode->i_sb->s_fsnotify_marks &&
200 	    (!mnt || !mnt->mnt_fsnotify_marks) && !parent_watched)
201 		return 0;
202 
203 	parent = NULL;
204 	parent_needed = fsnotify_event_needs_parent(inode, mnt, mask);
205 	if (!parent_watched && !parent_needed)
206 		goto notify;
207 
208 	/* Does parent inode care about events on children? */
209 	parent = dget_parent(dentry);
210 	p_inode = parent->d_inode;
211 	p_mask = fsnotify_inode_watches_children(p_inode);
212 	if (unlikely(parent_watched && !p_mask))
213 		__fsnotify_update_child_dentry_flags(p_inode);
214 
215 	/*
216 	 * Include parent/name in notification either if some notification
217 	 * groups require parent info or the parent is interested in this event.
218 	 */
219 	parent_interested = mask & p_mask & ALL_FSNOTIFY_EVENTS;
220 	if (parent_needed || parent_interested) {
221 		/* When notifying parent, child should be passed as data */
222 		WARN_ON_ONCE(inode != fsnotify_data_inode(data, data_type));
223 
224 		/* Notify both parent and child with child name info */
225 		take_dentry_name_snapshot(&name, dentry);
226 		file_name = &name.name;
227 		if (parent_interested)
228 			mask |= FS_EVENT_ON_CHILD;
229 	}
230 
231 notify:
232 	ret = fsnotify(mask, data, data_type, p_inode, file_name, inode, 0);
233 
234 	if (file_name)
235 		release_dentry_name_snapshot(&name);
236 	dput(parent);
237 
238 	return ret;
239 }
240 EXPORT_SYMBOL_GPL(__fsnotify_parent);
241 
fsnotify_handle_inode_event(struct fsnotify_group * group,struct fsnotify_mark * inode_mark,u32 mask,const void * data,int data_type,struct inode * dir,const struct qstr * name,u32 cookie)242 static int fsnotify_handle_inode_event(struct fsnotify_group *group,
243 				       struct fsnotify_mark *inode_mark,
244 				       u32 mask, const void *data, int data_type,
245 				       struct inode *dir, const struct qstr *name,
246 				       u32 cookie)
247 {
248 	const struct path *path = fsnotify_data_path(data, data_type);
249 	struct inode *inode = fsnotify_data_inode(data, data_type);
250 	const struct fsnotify_ops *ops = group->ops;
251 
252 	if (WARN_ON_ONCE(!ops->handle_inode_event))
253 		return 0;
254 
255 	if ((inode_mark->mask & FS_EXCL_UNLINK) &&
256 	    path && d_unlinked(path->dentry))
257 		return 0;
258 
259 	/* Check interest of this mark in case event was sent with two marks */
260 	if (!(mask & inode_mark->mask & ALL_FSNOTIFY_EVENTS))
261 		return 0;
262 
263 	return ops->handle_inode_event(inode_mark, mask, inode, dir, name, cookie);
264 }
265 
fsnotify_handle_event(struct fsnotify_group * group,__u32 mask,const void * data,int data_type,struct inode * dir,const struct qstr * name,u32 cookie,struct fsnotify_iter_info * iter_info)266 static int fsnotify_handle_event(struct fsnotify_group *group, __u32 mask,
267 				 const void *data, int data_type,
268 				 struct inode *dir, const struct qstr *name,
269 				 u32 cookie, struct fsnotify_iter_info *iter_info)
270 {
271 	struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
272 	struct fsnotify_mark *parent_mark = fsnotify_iter_parent_mark(iter_info);
273 	int ret;
274 
275 	if (WARN_ON_ONCE(fsnotify_iter_sb_mark(iter_info)) ||
276 	    WARN_ON_ONCE(fsnotify_iter_vfsmount_mark(iter_info)))
277 		return 0;
278 
279 	if (parent_mark) {
280 		/*
281 		 * parent_mark indicates that the parent inode is watching
282 		 * children and interested in this event, which is an event
283 		 * possible on child. But is *this mark* watching children and
284 		 * interested in this event?
285 		 */
286 		if (parent_mark->mask & FS_EVENT_ON_CHILD) {
287 			ret = fsnotify_handle_inode_event(group, parent_mark, mask,
288 							  data, data_type, dir, name, 0);
289 			if (ret)
290 				return ret;
291 		}
292 		if (!inode_mark)
293 			return 0;
294 	}
295 
296 	if (mask & FS_EVENT_ON_CHILD) {
297 		/*
298 		 * Some events can be sent on both parent dir and child marks
299 		 * (e.g. FS_ATTRIB).  If both parent dir and child are
300 		 * watching, report the event once to parent dir with name (if
301 		 * interested) and once to child without name (if interested).
302 		 * The child watcher is expecting an event without a file name
303 		 * and without the FS_EVENT_ON_CHILD flag.
304 		 */
305 		mask &= ~FS_EVENT_ON_CHILD;
306 		dir = NULL;
307 		name = NULL;
308 	}
309 
310 	return fsnotify_handle_inode_event(group, inode_mark, mask, data, data_type,
311 					   dir, name, cookie);
312 }
313 
send_to_group(__u32 mask,const void * data,int data_type,struct inode * dir,const struct qstr * file_name,u32 cookie,struct fsnotify_iter_info * iter_info)314 static int send_to_group(__u32 mask, const void *data, int data_type,
315 			 struct inode *dir, const struct qstr *file_name,
316 			 u32 cookie, struct fsnotify_iter_info *iter_info)
317 {
318 	struct fsnotify_group *group = NULL;
319 	__u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS);
320 	__u32 marks_mask = 0;
321 	__u32 marks_ignored_mask = 0;
322 	struct fsnotify_mark *mark;
323 	int type;
324 
325 	if (WARN_ON(!iter_info->report_mask))
326 		return 0;
327 
328 	/* clear ignored on inode modification */
329 	if (mask & FS_MODIFY) {
330 		fsnotify_foreach_obj_type(type) {
331 			if (!fsnotify_iter_should_report_type(iter_info, type))
332 				continue;
333 			mark = iter_info->marks[type];
334 			if (mark &&
335 			    !(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
336 				mark->ignored_mask = 0;
337 		}
338 	}
339 
340 	fsnotify_foreach_obj_type(type) {
341 		if (!fsnotify_iter_should_report_type(iter_info, type))
342 			continue;
343 		mark = iter_info->marks[type];
344 		/* does the object mark tell us to do something? */
345 		if (mark) {
346 			group = mark->group;
347 			marks_mask |= mark->mask;
348 			marks_ignored_mask |= mark->ignored_mask;
349 		}
350 	}
351 
352 	pr_debug("%s: group=%p mask=%x marks_mask=%x marks_ignored_mask=%x data=%p data_type=%d dir=%p cookie=%d\n",
353 		 __func__, group, mask, marks_mask, marks_ignored_mask,
354 		 data, data_type, dir, cookie);
355 
356 	if (!(test_mask & marks_mask & ~marks_ignored_mask))
357 		return 0;
358 
359 	if (group->ops->handle_event) {
360 		return group->ops->handle_event(group, mask, data, data_type, dir,
361 						file_name, cookie, iter_info);
362 	}
363 
364 	return fsnotify_handle_event(group, mask, data, data_type, dir,
365 				     file_name, cookie, iter_info);
366 }
367 
fsnotify_first_mark(struct fsnotify_mark_connector ** connp)368 static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp)
369 {
370 	struct fsnotify_mark_connector *conn;
371 	struct hlist_node *node = NULL;
372 
373 	conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
374 	if (conn)
375 		node = srcu_dereference(conn->list.first, &fsnotify_mark_srcu);
376 
377 	return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
378 }
379 
fsnotify_next_mark(struct fsnotify_mark * mark)380 static struct fsnotify_mark *fsnotify_next_mark(struct fsnotify_mark *mark)
381 {
382 	struct hlist_node *node = NULL;
383 
384 	if (mark)
385 		node = srcu_dereference(mark->obj_list.next,
386 					&fsnotify_mark_srcu);
387 
388 	return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
389 }
390 
391 /*
392  * iter_info is a multi head priority queue of marks.
393  * Pick a subset of marks from queue heads, all with the
394  * same group and set the report_mask for selected subset.
395  * Returns the report_mask of the selected subset.
396  */
fsnotify_iter_select_report_types(struct fsnotify_iter_info * iter_info)397 static unsigned int fsnotify_iter_select_report_types(
398 		struct fsnotify_iter_info *iter_info)
399 {
400 	struct fsnotify_group *max_prio_group = NULL;
401 	struct fsnotify_mark *mark;
402 	int type;
403 
404 	/* Choose max prio group among groups of all queue heads */
405 	fsnotify_foreach_obj_type(type) {
406 		mark = iter_info->marks[type];
407 		if (mark &&
408 		    fsnotify_compare_groups(max_prio_group, mark->group) > 0)
409 			max_prio_group = mark->group;
410 	}
411 
412 	if (!max_prio_group)
413 		return 0;
414 
415 	/* Set the report mask for marks from same group as max prio group */
416 	iter_info->report_mask = 0;
417 	fsnotify_foreach_obj_type(type) {
418 		mark = iter_info->marks[type];
419 		if (mark &&
420 		    fsnotify_compare_groups(max_prio_group, mark->group) == 0)
421 			fsnotify_iter_set_report_type(iter_info, type);
422 	}
423 
424 	return iter_info->report_mask;
425 }
426 
427 /*
428  * Pop from iter_info multi head queue, the marks that were iterated in the
429  * current iteration step.
430  */
fsnotify_iter_next(struct fsnotify_iter_info * iter_info)431 static void fsnotify_iter_next(struct fsnotify_iter_info *iter_info)
432 {
433 	int type;
434 
435 	fsnotify_foreach_obj_type(type) {
436 		if (fsnotify_iter_should_report_type(iter_info, type))
437 			iter_info->marks[type] =
438 				fsnotify_next_mark(iter_info->marks[type]);
439 	}
440 }
441 
442 /*
443  * fsnotify - This is the main call to fsnotify.
444  *
445  * The VFS calls into hook specific functions in linux/fsnotify.h.
446  * Those functions then in turn call here.  Here will call out to all of the
447  * registered fsnotify_group.  Those groups can then use the notification event
448  * in whatever means they feel necessary.
449  *
450  * @mask:	event type and flags
451  * @data:	object that event happened on
452  * @data_type:	type of object for fanotify_data_XXX() accessors
453  * @dir:	optional directory associated with event -
454  *		if @file_name is not NULL, this is the directory that
455  *		@file_name is relative to
456  * @file_name:	optional file name associated with event
457  * @inode:	optional inode associated with event -
458  *		either @dir or @inode must be non-NULL.
459  *		if both are non-NULL event may be reported to both.
460  * @cookie:	inotify rename cookie
461  */
fsnotify(__u32 mask,const void * data,int data_type,struct inode * dir,const struct qstr * file_name,struct inode * inode,u32 cookie)462 int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir,
463 	     const struct qstr *file_name, struct inode *inode, u32 cookie)
464 {
465 	const struct path *path = fsnotify_data_path(data, data_type);
466 	struct fsnotify_iter_info iter_info = {};
467 	struct super_block *sb;
468 	struct mount *mnt = NULL;
469 	struct inode *parent = NULL;
470 	int ret = 0;
471 	__u32 test_mask, marks_mask;
472 
473 	if (path)
474 		mnt = real_mount(path->mnt);
475 
476 	if (!inode) {
477 		/* Dirent event - report on TYPE_INODE to dir */
478 		inode = dir;
479 	} else if (mask & FS_EVENT_ON_CHILD) {
480 		/*
481 		 * Event on child - report on TYPE_PARENT to dir if it is
482 		 * watching children and on TYPE_INODE to child.
483 		 */
484 		parent = dir;
485 	}
486 	sb = inode->i_sb;
487 
488 	/*
489 	 * Optimization: srcu_read_lock() has a memory barrier which can
490 	 * be expensive.  It protects walking the *_fsnotify_marks lists.
491 	 * However, if we do not walk the lists, we do not have to do
492 	 * SRCU because we have no references to any objects and do not
493 	 * need SRCU to keep them "alive".
494 	 */
495 	if (!sb->s_fsnotify_marks &&
496 	    (!mnt || !mnt->mnt_fsnotify_marks) &&
497 	    (!inode || !inode->i_fsnotify_marks) &&
498 	    (!parent || !parent->i_fsnotify_marks))
499 		return 0;
500 
501 	marks_mask = sb->s_fsnotify_mask;
502 	if (mnt)
503 		marks_mask |= mnt->mnt_fsnotify_mask;
504 	if (inode)
505 		marks_mask |= inode->i_fsnotify_mask;
506 	if (parent)
507 		marks_mask |= parent->i_fsnotify_mask;
508 
509 
510 	/*
511 	 * if this is a modify event we may need to clear the ignored masks
512 	 * otherwise return if none of the marks care about this type of event.
513 	 */
514 	test_mask = (mask & ALL_FSNOTIFY_EVENTS);
515 	if (!(mask & FS_MODIFY) && !(test_mask & marks_mask))
516 		return 0;
517 
518 	iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
519 
520 	iter_info.marks[FSNOTIFY_OBJ_TYPE_SB] =
521 		fsnotify_first_mark(&sb->s_fsnotify_marks);
522 	if (mnt) {
523 		iter_info.marks[FSNOTIFY_OBJ_TYPE_VFSMOUNT] =
524 			fsnotify_first_mark(&mnt->mnt_fsnotify_marks);
525 	}
526 	if (inode) {
527 		iter_info.marks[FSNOTIFY_OBJ_TYPE_INODE] =
528 			fsnotify_first_mark(&inode->i_fsnotify_marks);
529 	}
530 	if (parent) {
531 		iter_info.marks[FSNOTIFY_OBJ_TYPE_PARENT] =
532 			fsnotify_first_mark(&parent->i_fsnotify_marks);
533 	}
534 
535 	/*
536 	 * We need to merge inode/vfsmount/sb mark lists so that e.g. inode mark
537 	 * ignore masks are properly reflected for mount/sb mark notifications.
538 	 * That's why this traversal is so complicated...
539 	 */
540 	while (fsnotify_iter_select_report_types(&iter_info)) {
541 		ret = send_to_group(mask, data, data_type, dir, file_name,
542 				    cookie, &iter_info);
543 
544 		if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
545 			goto out;
546 
547 		fsnotify_iter_next(&iter_info);
548 	}
549 	ret = 0;
550 out:
551 	srcu_read_unlock(&fsnotify_mark_srcu, iter_info.srcu_idx);
552 
553 	return ret;
554 }
555 EXPORT_SYMBOL_GPL(fsnotify);
556 
fsnotify_init(void)557 static __init int fsnotify_init(void)
558 {
559 	int ret;
560 
561 	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 25);
562 
563 	ret = init_srcu_struct(&fsnotify_mark_srcu);
564 	if (ret)
565 		panic("initializing fsnotify_mark_srcu");
566 
567 	fsnotify_mark_connector_cachep = KMEM_CACHE(fsnotify_mark_connector,
568 						    SLAB_PANIC);
569 
570 	return 0;
571 }
572 core_initcall(fsnotify_init);
573